Electrical Impedance Tomography (ElT) has been used as a visualisation
and measurement tool in many fields such as medical imaging, geophysical
prospecting and industrial process applications. To date, single sensing ring
strategies and two-dimensional (2D) electric field reconstruction algorithms
are mostly used in ElT applications. The quality of measurement will be
affected by the three-dimensional (3D) effects that cause imaging errors in
both the near-sensor-region and the spatial coordination of a conventional
2D sensor. The typical errors include the object off-plane sensing and offpath
trajectory effects - objects lying a short axial distance from the image
plane are reconstructed closer to the central axis than their true position.
There is a distinct possibility that it may also give a rise to erroneous velocity
components normal to the axial direction.
The aim of this thesis is to reduce the 3D effects by designing and
implementing a full 3D pipeline sensing strategy which takes into account of
the 3D nature of the ElT sensing field. The main approaches of the thesis
are: (1) a new sensing system, the Zigzag sensor, which represents a new
electrode configuration has been designed; (2) a fast forward solver, using
Finite Element Modelling, has been implemented with the aim of achieving
real-time processing of tomographic measurements; (3) the Sensitivity
Conjugate Gradient (SCG) Algorithm has been adapted to 3D ElT for the
first time. Moreover, the thesis contributes towards the application of the
developed 3D ElT system for dynamic flow visualisation and velocimetry
with 3D auto-correlation method which provided a balance between the
requested imaging precision and computation speed.
The thesis details both theoretical and experimental approaches as well as
evidences that the zigzag sensor with the 3D SCG offers some advantage
over conventional methods to reduce the 3D effects on ElT pipeline imaging.